✅ Can't get `InternalsVisibleTo` to work

From assembly (project)

A.B

A.B

I added the following in a file

using System.Runtime.CompilerServices;

[assembly: InternalsVisibleTo("A.B.Tests")]

namespace MyNamespace
{
    internal class MyClass {}
}

using System.Runtime.CompilerServices;

[assembly: InternalsVisibleTo("A.B.Tests")]

namespace MyNamespace
{
    internal class MyClass {}
}

But the assembly

A.B.Test

A.B.Test

can't see

MyClass

MyClass

.
Is there something extra that I should do?